Clumps of the gooseneck barnacle Pollicipes elegans were found in the central Pacific on a rocky shore of Costa Rica. This species is known to be abundant in northern and southern latitudes of the eastern tropical Pacific. This study describes aspects of its demography and size structure, as well as habitat features in Costa Rica. The clumps were generally on vertical rocky substrates, with a negative slope and an average height of 1.70 m above the Lowest Astronomical Tide. Two cohorts were found on the rocky shore in 2014. An important decline of abundance and density of clumps was found between July and October of 2014. Additional clumps were found in September 2016. We present hypotheses about how this species became established in Costa Rica and why a decline of the clumps was observed.